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Fewer Shots Of HPV Vaccine May Still Protect Against Cancer

Women who didn't get all three doses of HPV vaccine, as is recommended, were still protected against the virus that causes cervical cancer, a new study finds. If that result holds up, it could become easier and less expensive to protect women against this common form of cancer.

Three doses of the vaccine within six months are currently recommended. In this study, which is part of ongoing research on the HPV vaccine in Costa Rica, about 20 percent of the women didn't get all three shots because they got pregnant or had other medical issues. Half the women in the study were randomly assigned to receive Cerverix, an HPV vaccine from GlaxoSmithKline, or a vaccine against hepatitis A.

When women who had gotten one or two shots of Cerverix were tested for HPV infection, they were just as well protected after four years as women who received the full regimen.

The United States added the HPV vaccine to recommended vaccinations for teenage girls in 2006. But only about 32 percent of 13- to 17-year-old girls have gotten all three shots.

The three-shot series is inconvenient, since girls need to make three trips to the doctor's office for the full series. And it's expensive — about $400. So if two shots, or even one shot, would do, vaccination would be simpler and cheaper. That's particularly true for women in developing countries, who often don't have access to frequent screening checkups such as Pap smears.

But this study has followed the young women who are participating for just four years so far, and women need to be protected from their teens up into their 20s, according to Aimee Kreimer, an investigator at the National Cancer Institute, and lead author on the study. "We need to protect them during the main time of sexual activity," she told Shots. "There's a concern that the duration of the protection for fewer than three doses will not be as long."

The study, which was published in the Journal of the National Cancer Institute, will follow the 7,153 women in the study for another six years, Kreimer says. "But really, 15 years would be ideal." That would give young women and their doctors a much clearer sense of whether three doses are really needed for protection.

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